Hi John, I am unable to reproduce the scenario you are describing, but from your debug data it looks clear enough: a STATE packet with ack value !=0 has bypassed the first in-sequence packets, which still have an invalid pre-synch ack value.
If that diagnosis is right, this patch should solve the problem. Please test this and give feedback. BR ///jon > -----Original Message----- > From: Jon Maloy [mailto:jon.ma...@ericsson.com] > Sent: Wednesday, 07 September, 2016 08:18 > To: tipc-discussion@lists.sourceforge.net; Parthasarathy Bhuvaragan > <parthasarathy.bhuvara...@ericsson.com>; Ying Xue > <ying....@windriver.com>; Richard Alpe <richard.a...@ericsson.com>; Jon > Maloy <jon.ma...@ericsson.com> > Cc: ma...@donjonn.com; gbala...@gmail.com > Subject: [PATCH net 1/1] tipc: fix broadcast link synchronization problem > > In commit 2d18ac4ba745 ("tipc: extend broadcast link initialization > criteria") we tried to fix a problem with the initial synchronization > of broadcast link acknowledge values. Unfortunately that solution is > not sufficient to solve the problem. > > We have seen it happen that a LINK_PROTOCOL/STATE message with a valid > non-zero unicast acknowledge number may bypass BCAST_PROTOCOL > initialization and NAME_DISRIBUTOR packets with invalid broadcast > acknowledge numbers, leading to premature opening of the broadcast link. > When this happens, the already correctly initialized acknowledge number > of the broadcast receive link will be overwritten by the invalid (zero) > value of the said packets, and the broadcast link risks going stale. > > We now fix this by ignoring acknowledges that we know potentially may > be invalid. Identifying such acknowledges is easy, since their broadcast > acknowledge value always is zero, and since this can only happen to > BCAST_PROTOCOL and NAME_DISTRIBUTOR messages. > > Reported-by: John Thompson <thompa....@gmail.com> > Signed-off-by: Jon Maloy <jon.ma...@ericsson.com> > --- > net/tipc/bcast.c | 7 ++++++- > net/tipc/bcast.h | 3 ++- > net/tipc/node.c | 2 +- > 3 files changed, 9 insertions(+), 3 deletions(-) > > diff --git a/net/tipc/bcast.c b/net/tipc/bcast.c > index ae469b3..27ffa37 100644 > --- a/net/tipc/bcast.c > +++ b/net/tipc/bcast.c > @@ -247,11 +247,16 @@ int tipc_bcast_rcv(struct net *net, struct tipc_link *l, > struct sk_buff *skb) > * > * RCU is locked, no other locks set > */ > -void tipc_bcast_ack_rcv(struct net *net, struct tipc_link *l, u32 acked) > +void tipc_bcast_ack_rcv(struct net *net, struct tipc_link *l, > + int usr, u16 acked) > { > struct sk_buff_head *inputq = &tipc_bc_base(net)->inputq; > struct sk_buff_head xmitq; > > + /* Ignore acks potentially sent before bcast synch point was received */ > + if (!acked && ((usr == BCAST_PROTOCOL) || (usr == > NAME_DISTRIBUTOR))) > + return; > + > __skb_queue_head_init(&xmitq); > > tipc_bcast_lock(net); > diff --git a/net/tipc/bcast.h b/net/tipc/bcast.h > index d5e79b3..0529cb5 100644 > --- a/net/tipc/bcast.h > +++ b/net/tipc/bcast.h > @@ -55,7 +55,8 @@ void tipc_bcast_dec_bearer_dst_cnt(struct net *net, int > bearer_id); > int tipc_bcast_get_mtu(struct net *net); > int tipc_bcast_xmit(struct net *net, struct sk_buff_head *list); > int tipc_bcast_rcv(struct net *net, struct tipc_link *l, struct sk_buff > *skb); > -void tipc_bcast_ack_rcv(struct net *net, struct tipc_link *l, u32 acked); > +void tipc_bcast_ack_rcv(struct net *net, struct tipc_link *l, > + int usr, u16 acked); > void tipc_bcast_sync_rcv(struct net *net, struct tipc_link *l, > struct tipc_msg *hdr); > int tipc_nl_add_bc_link(struct net *net, struct tipc_nl_msg *msg); > diff --git a/net/tipc/node.c b/net/tipc/node.c > index 2197419..42f98af 100644 > --- a/net/tipc/node.c > +++ b/net/tipc/node.c > @@ -1507,7 +1507,7 @@ void tipc_rcv(struct net *net, struct sk_buff *skb, > struct > tipc_bearer *b) > if (unlikely(usr == LINK_PROTOCOL)) > tipc_bcast_sync_rcv(net, n->bc_entry.link, hdr); > else if (unlikely(tipc_link_acked(n->bc_entry.link) != bc_ack)) > - tipc_bcast_ack_rcv(net, n->bc_entry.link, bc_ack); > + tipc_bcast_ack_rcv(net, n->bc_entry.link, usr, bc_ack); > > /* Receive packet directly if conditions permit */ > tipc_node_read_lock(n); > -- > 2.7.4 ------------------------------------------------------------------------------ _______________________________________________ tipc-discussion mailing list tipc-discussion@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/tipc-discussion
